The present invention relates to a novel glycosphingolipid and applications thereof, and more specifically to a novel glycosphingolipid having a characteristic structure in the sugar portion thereof, and its applications as cosmetics and pharmaceuticals.
Rough skin is caused by excessive loss of moisture from the surface of the skin exposed to dry air or cleansing. In these days, various environmental chemical substances may also inhibit skin functions such as lipid secretion, which results in rough skin. Therefore, there is a demand for providing a substance capable of preventing rough skin and having an excellent moisturizing effect.
Various active compounds having a moisturizing effect have been provided, which mainly comprise water-soluble polyols. Some of them including propylene glycols have already been commercialized. However, many of commercialized moisturizing compounds are associated with uncomfortable feel when they are applied or only available with insufficient moisturizing effect, so that there is still a strong demand for the development of a new moisturizing compound.
In such situation, glycosphingolipid attracts a great deal of attention as a safe moisturizing compound.
For example, Japanese Laid-Open Patent Publication Nos. 1-242690, 2-48520 and 4-159203, and Japanese Examined Patent Publication No. 6-80007 describe that glycosphingolipid has skin moisturizing effect. Japanese Laid-Open Patent Publication No. 6-157283 discloses a skin moisturizing cosmetic for external use containing as one ingredient a glycosphingolipid expressed by a specific general formula. Details of the structures of such glycosphingolipids disclosed in the foregoing publications have, however, been not clear.
Japanese Laid-Open Patent Publication No. 61-286307 is one literature specifically defines a glycosphingolipid having moisturizing effect. The publication describes that ganglioside has skin moisturizing effect and emollient effect, and discloses a skin cosmetic containing ganglioside and a salt thereof. Ganglioside is a kind of glycosphingolipid containing amino sugars and sialic acid besides neutral sugars.
Japanese Laid-Open Patent Publication Nos. 5-39485, 7-133217 and 7-285827 disclose skin agents for external use containing cerebroside. Cerebroside is a kind of glycosphingolipid comprising each one mol of fatty acid, sphingosine base and neutral sugar (galactose or glucose).
Japanese Laid-Open Patent Publication No. 11-43437 describes that a glycosphingolipid having a specific structure has moisturizing effect, whose sugar chain is limited to that containing 1 to 4 hexoses selected from the group comprising uronic acid, glucosamine, galactose and mannose, as combined with one uronic acid.
As has been described in the above, while several kinds of structures have been defined as for glycosphingolipid having moisturizing effect, there is still a need for providing a novel glycosphingolipid having a novel structure. In particular, most strong need resides in that providing a novel glycosphingolipid having moisturizing effect and other miscellaneous activities, and is possibly be manufactured in a relatively facile manner.
Considering such prior art, it is therefore an object of the present invention to provide a glycosphingolipid having a novel structure, and more particularly to provide a glycosphingolipid having moisturizing effect and other miscellaneous activities, and is possibly be manufactured in a relatively facile manner.
The present inventors found out that a novel glycosphingolipid is contained in components of a somatic extract from bacterium Sphingomonas sp., which led us to complete the present invention.
That is, the present invention provides a glycosphingolipid having a sugar chain containing xcex1-glucosamine and xcex2-glucosamine.
The sugar chain preferably comprises mannose, xcex2-glucosamine, xcex1-glucosamine and glucuronic acid, and more preferably has a structure expressed by formula (A) below:
xcex1-Man-(1xe2x86x923)-xcex2-GlcN-(1xe2x86x926)-xcex1-GlcN-(1xe2x86x924)-xcex1-GlcAxe2x80x83xe2x80x83(A)
(where, Man represents mannose, GlcN represents glucosamine and GlcA represents glucuronic acid).
The glycosphingolipid of the present invention is particularly preferable if it has a structure expressed by the formula below: 
(where, R1 represents the sugar chain containing xcex1-glucosamine and xcex2-glucosamine, R2 represents any one of an alkyl group possibly having cycloalkyl group, an alkenyl group and an alkynyl group; R3 represents an alkyl group; all of such alkyl group, alkenyl group and alkynyl group may be straight or branched, and may be substituted or unsubstituted).
R2 preferably has a carbon number of 15 to 25, and more preferably has a structure expressed by any one of the formulae below. It should now be noted that a numerical range expressed with a word xe2x80x9ctoxe2x80x9d in this specification includes both end values as a minimum value and a maximum value, respectively. 
R3 is preferably a substituted or unsubstituted straight alkyl group having a carbon number of 10 to 20, and more preferably a straight alkyl group having a carbon number of 12.
The present invention also provides a cosmetic and a pharmaceutical composition containing such glycosphingolipid, in particular a moisturizer and an immuno-enhancer.